Nec­es­sary infor­ma­tion about radi­a­tors made of alu­minum and bimet­al

By appoint­ment, a radi­a­tor is a unit with the help of which a cer­tain space inside a room is heat­ed. By design, as a rule, it con­sists of sev­er­al sec­tions, in each of them the coolant cir­cu­lates. Accord­ing to the pro­duc­tion method, a spe­cial alu­minum alloy is poured into molds. These forms are made in the form of sec­tions, which are lat­er con­nect­ed into a sin­gle sys­tem. In the 21st cen­tu­ry, there should not be any dif­fi­cul­ty in man­u­fac­tur­ing a heat­ing radi­a­tor from alu­minum. Why does it seem that such a “house­hold” device as a heat­ing radi­a­tor is still clas­si­fied by experts as a high-tech prod­uct?

The best experts in the pro­duc­tion of these prod­ucts and sci­en­tif­ic con­sul­tants of the heat­ing appli­ance indus­try com­mu­ni­ty will tell us about the intri­ca­cies of man­u­fac­tur­ing alu­minum and bimetal­lic radi­a­tors.

The main types and fea­tures of mod­ern heat­ing radi­a­tors

In total, there are 3 types of alu­minum radi­a­tors: cast, extrud­ed and com­bined. Each species has its own pro­duc­tion nuances.

Cast radi­a­tors con­sist of one-piece cast sec­tions made under high pres­sure, with each such sec­tion being formed in a mold. Then they are con­nect­ed into a sin­gle radi­a­tor using spe­cial nip­ples. To seal the inter­sec­tion joints, gas­kets made of graphite or paronite, high-tem­per­a­ture sil­i­cone or oth­er mate­ri­als are used.

One piece extru­sion heatsinks made of extrud­ed alu­minum pro­files. As the name sug­gests, such pro­files are made by extru­sion: an alu­minum alloy is pressed through the molds, after which all the indi­vid­ual ele­ments are joined togeth­er by weld­ing. Such radi­a­tors are non-sep­a­ra­ble by their design.

Com­bined alu­minum radi­a­tors com­bine the prop­er­ties of the cast and extru­sion radi­a­tors list­ed above. Sec­tions are made of extrud­ed pro­files, and ele­ments of hor­i­zon­tal col­lec­tors are made by injec­tion mold­ing.

There is also anoth­er type that ensures sta­ble oper­a­tion under con­di­tions of high work­ing pres­sure — this is bimetal­lic radi­a­tors. The dif­fer­ence from all-alu­minum is the pres­ence of a mort­gage ele­ment — a steel man­i­fold. Sec­tions of this type of radi­a­tor for cen­tral heat­ing con­sist of a steel core in the form of thin-walled steel pipes (chan­nel for the pas­sage of the coolant) with exter­nal alu­minum alloy fins that per­form the func­tion of heat trans­fer. This is done so that the coolant (water) pass­es through the col­lec­tor with­out con­tact with alu­minum.


In the pro­duc­tion of radi­a­tors, they are pri­mar­i­ly guid­ed by the require­ments of com­pli­ance with GOST 31311–2015 “Heat­ing appli­ances. Gen­er­al tech­ni­cal conditions»[1].

The most impor­tant indi­ca­tor of safe­ty is sta­t­ic strength, which is ensured by:

— use of high-qual­i­ty alu­minum ingots;

— use of mod­ern melt­ing fur­naces and com­pli­ance with the melt prepa­ra­tion tech­nol­o­gy;

— func­tion­ing of mod­ern cast­ing machines and fixed cast­ing modes;

— the use of molds of a spe­cial design that pro­vides cool­ing and removal of gas­es;

— avail­abil­i­ty of a spec­tral analy­sis lab­o­ra­to­ry for input con­trol of raw mate­ri­als and melt qual­i­ty;

— work of qual­i­fied per­son­nel (includ­ing tech­nol­o­gists and oper­a­tors of cast­ing machines).

In accor­dance with GOST R 53583–2009 “Heat­ing appli­ances. Test Meth­ods» [2] in spe­cial­ized lab­o­ra­to­ries that have the nec­es­sary equip­ment to mea­sure heat trans­fer, strength and tight­ness, they car­ry out the nec­es­sary tests to con­firm the con­sumer prop­er­ties of the radi­a­tor declared by the man­u­fac­tur­er.

It should be not­ed that at the moment there is no manda­to­ry cer­ti­fi­ca­tion of heat­ing radi­a­tors, there­fore all the require­ments of GOST 31311–2005 are “good man­ners” for radi­a­tor man­u­fac­tur­ers. They are observed by con­sci­en­tious man­u­fac­tur­ers on a vol­un­tary basis.

Are all alloys iden­ti­cal?

GOST 31311–2005 states that cast alu­minum radi­a­tors must be made from alu­minum alloys that pro­vide the required tech­no­log­i­cal and struc­tur­al para­me­ters of the cast­ings.

The chem­i­cal com­po­si­tion of the alu­minum alloy sig­nif­i­cant­ly affects the ther­mal and tech­no­log­i­cal prop­er­ties of the radi­a­tor. In accor­dance with GOST, the alloy of the mate­r­i­al is charged (formed) with var­i­ous addi­tives to achieve the required com­po­si­tion.

The link between pro­duc­tion and tech­nol­o­gy plays an impor­tant role. In a spe­cif­ic pro­duc­tion, they must adhere to a spe­cif­ic tech­nol­o­gy devel­oped and exist­ing there. One of the main fac­tors affect­ing the qual­i­ty of the final prod­uct is the cor­rect design of the sys­tem of chan­nels and cav­i­ties in the mold, since alu­minum alloys are sub­ject to very strong oxi­da­tion.

In prin­ci­ple, the basis of alu­minum is the same, dif­fer­ing only in the num­ber of com­po­nents in the alloy. Sep­a­rate­ly tak­en pro­duc­tion selects a cer­tain alloy for spe­cif­ic tasks. Depend­ing on the man­u­fac­tured mod­els of radi­a­tors, the chem­i­cal ele­ments of the mate­r­i­al make it pos­si­ble to achieve the desired phys­i­cal and mechan­i­cal prop­er­ties of the final prod­uct.

Espe­cial­ly for such tasks at good man­u­fac­tur­ing plants, it is pos­si­ble to vary the impu­ri­ties added to the alu­minum alloy. First of all, such is sil­i­con, an increase in the con­tent of which helps to improve the cast­ing prop­er­ties of the alloy, to give it greater flu­id­i­ty. Due to this prop­er­ty, man­u­fac­tur­ers have the oppor­tu­ni­ty to cast a radi­a­tor with a thin­ner fin width. As a result, the mass of the radi­a­tor is reduced (the sur­face area does not change, but the amount of mate­r­i­al used for man­u­fac­tur­ing is less). How­ev­er, it should be borne in mind that with such a pro­ce­dure, heat trans­fer will also decrease.

What stan­dards should be pro­vid­ed for in the prepa­ra­tion of melts? This is degassing, con­trol of the tem­per­a­ture of the melt and its chem­i­cal com­po­si­tion.

What defects can occur dur­ing the melt­ing of ingots and cast­ing of fin­ished prod­ucts (affect­ing the qual­i­ty of the prod­uct and its strength)? It:

— pores, air sat­u­ra­tion,

— inclu­sions,

— sur­face defects,

— low strength and duc­til­i­ty,

— sinks, shrink­age and some oth­ers.

What para­me­ters should be mon­i­tored? For cast radi­a­tors, this is the con­trol of the wall thick­ness, and in the pro­duc­tion of bimetal­lic radi­a­tors, it is the con­trol of the posi­tion­ing of the embed­ded ele­ment.

Radi­a­tor Spec­i­fi­ca­tions

First of all, it is nec­es­sary to judge the good qual­i­ty of the radi­a­tor by the nom­i­nal heat flux (heat out­put). THeat flow is the pow­er of ther­mal ener­gy com­ing from the heat­ing device. Anoth­er qual­i­ty is evi­denced by such a char­ac­ter­is­tic as pwork­ing pres­sure. Oper­at­ing pres­sure — this is the max­i­mum over­pres­sure in the heat­ing sys­tem that the radi­a­tor design can with­stand.

Accord­ing to GOST 31311–2005, radi­a­tors must be strong and tight enough to with­stand a test pres­sure one and a half times the max­i­mum oper­at­ing pres­sure. In this case, the destruc­tion pres­sure for cast radi­a­tors must exceed the max­i­mum oper­at­ing pres­sure by at least three times. Also, the norms for the per­mis­si­ble devi­a­tion of the actu­al val­ue also exist for heat trans­fer. They are estab­lished accord­ing to the results of the tests. The val­ue declared by the man­u­fac­tur­er on the pack­ag­ing and in the accom­pa­ny­ing doc­u­men­ta­tion (in the tech­ni­cal data sheet of the device) must be in the range from ‑4% to +5%.

In addi­tion, it is nec­es­sary to take into account a num­ber of fac­tors that affect the val­ue of the heat trans­fer of the heater. Accord­ing to many years of research by the MRT lab­o­ra­to­ry of the Poly­tech­nic Uni­ver­si­ty of Milan (Politec­ni­co di Milano), as well as the lead­ing Russ­ian test­ing lab­o­ra­to­ries for heat­ing devices of the Research Insti­tute of Plumb­ing and Vitaterm, a cer­tain depen­dence of the heat out­put of the radi­a­tor on the mate­r­i­al, shape, thick­ness, sur­face treat­ment tech­nol­o­gy, and on the para­me­ters of the cir­cu­la­tion of the coolant inside prod­ucts.

Qual­i­ty and its con­trol

Since heat­ing radi­a­tors are over­whelm­ing­ly locat­ed in res­i­den­tial and pub­lic build­ings, in oth­er words, they are in close prox­im­i­ty to peo­ple, in con­nec­tion with this cir­cum­stance, uni­form reg­u­la­to­ry require­ments should be imposed on their safe­ty and qual­i­ty.

Even at the man­u­fac­tur­ing stage, the man­u­fac­tur­ers them­selves car­ry out a thor­ough qual­i­ty check of heat­ing radi­a­tors. Pro­duc­tion con­trol is mul­ti­fac­to­r­i­al and mul­ti­stage.

The first stage of con­trol — qual­i­ty con­trol is includ­ed in the offi­cial duties of the staff: that is, for the work­er, and for the fore­man, and for the shift super­vi­sor, one of the main moti­va­tions is the release of high-qual­i­ty prod­ucts.

The sec­ond lev­el of con­trol is the tech­no­log­i­cal ser­vice, which devel­ops the pro­duc­tion tech­nol­o­gy for each pro­duc­tion oper­a­tion and takes care of com­pli­ance with the approved tech­no­log­i­cal maps.

The third degree of con­trol is a spe­cial qual­i­ty ser­vice that car­ries out direct con­trol at each stage of pro­duc­tion, as well as com­plete input con­trol of the mate­r­i­al from which the prod­ucts will be made (spec­tro­graph­ic con­trol): it is sim­ply impos­si­ble to smelt a good qual­i­ty met­al with­out prompt ver­i­fi­ca­tion of com­pli­ance with the chem­i­cal com­po­si­tion of the alloy. Such ver­i­fi­ca­tion accord­ing to the norms is car­ried out in the lab­o­ra­to­ries of spec­tral analy­sis.

In addi­tion, the qual­i­ty ser­vice should be equipped with equip­ment to check the geo­met­ric dimen­sions of sec­tions, wall thick­ness, thread qual­i­ty, as well as to check the tight­ness and strength of sec­tions and radi­a­tors as a whole.

In Europe, in turn, the expe­ri­ence of qual­i­ty con­trol in the pro­duc­tion of radi­a­tors is tra­di­tion­al­ly adopt­ed from Italy, as it is at the head of the list that pro­duces first-class heat­ing appli­ances. The Euro­pean man­u­fac­tur­er is oblig­ed to car­ry out fac­to­ry pro­duc­tion con­trol (FPC) to ensure that the prod­ucts sold com­ply with the main para­me­ters of the Dec­la­ra­tion of Per­for­mance (DoP) (sim­i­lar to our Russ­ian heater pass­port). Such a sys­tem of pro­duc­tion con­trol ensures the achieve­ment of excel­lent qual­i­ty and the required tech­ni­cal char­ac­ter­is­tics of prod­ucts at the high­est lev­el.

From every­thing we can con­clude that in order to pro­duce high qual­i­ty alu­minum or bimetal­lic radi­a­tors, the man­u­fac­tur­er needs to have deep knowl­edge, skills and abil­i­ties in wide areas of mechan­i­cal engi­neer­ing, met­al­lur­gy and met­al­work­ing, reli­able mod­ern equip­ment and high­ly qual­i­fied per­son­nel.

And in par­al­lel with strict qual­i­ty con­trol and observ­ing safe­ty require­ments, it is pos­si­ble to pro­duce a reli­able and ener­gy-effi­cient heat­ing radi­a­tor. At the same time, it is obvi­ous that only by fol­low­ing state stan­dards can a high result be achieved.

The arti­cle was pre­pared by APRO spe­cial­ists.

Thank you for your help in prepar­ing this arti­cle:

Gian­lui­gi Ari­ci, Deputy Chair­man of the Asso­ci­a­tion of Man­u­fac­tur­ers of Equip­ment and Com­po­nents for Heat­ing Sys­tems Assoter­mi­ca;

- Ren­zo March­esiHead of the Ther­mal Engi­neer­ing Research Lab­o­ra­to­ry MRT (Mis­ure Ricerche Ter­motec­niche) of the Politec­ni­co di Milano;

Clau­dio Tari­niTher­mal Engi­neer­ing Research Lab­o­ra­to­ry MRT (Mis­ure Ricerche Ter­motec­niche) of the Politec­ni­co di Milano;

- Vitaly Sasi­na, Gen­er­al Direc­tor of the test­ing lab­o­ra­to­ry “Vitaterm”;

Vasi­ly Gro­mov, pro­fes­sor of MAN, sci­en­tif­ic sec­re­tary of the Research Insti­tute of San­i­tary Engi­neer­ing;

- Her­man Bershid­sky, Deputy Gen­er­al Direc­tor of the Research Insti­tute of San­i­tary Engi­neer­ing for Sci­ence;

- Niko­lai Salivonchik, Deputy Gen­er­al Direc­tor of the largest Belaru­sian pro­duc­tion of alu­minum radi­a­tors;

- Petra Smirno­va, direc­tor of strate­gic devel­op­ment of the Roy­al Ther­mo Indus­tri­al Group — Cam­po Di Calore;

Max­im TorunovDeputy Head of Pro­duc­tion of the Indus­tri­al Group Roy­al Ther­mo — Cam­po Di Calore.

  1. Inter­state stan­dard GOST 31311–2005. Heat­ing devices. Gen­er­al spec­i­fi­ca­tions. — M .: “Stan­dart­in­form”, 2006.

  2. Nation­al stan­dard of the Russ­ian Fed­er­a­tion GOST R 53583–2009. Heat­ing devices. Test meth­ods. — M. “Stan­dart­in­form”, 2010.

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